diff --git a/common/test_utils.h b/common/test_utils.h
index ba9f5f2..ddb3d34 100644
--- a/common/test_utils.h
+++ b/common/test_utils.h
@@ -31,6 +31,7 @@
 #include <base/callback.h>
 #include <base/files/file_path.h>
 #include <base/files/scoped_temp_dir.h>
+#include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
 #include "update_engine/common/action.h"
@@ -101,6 +102,11 @@
 
 void FillWithData(brillo::Blob* buffer);
 
+// Compare the value of native array for download source parameter.
+MATCHER_P(DownloadSourceMatcher, source_array, "") {
+  return std::equal(source_array, source_array + kNumDownloadSources, arg);
+}
+
 // Class to unmount FS when object goes out of scope
 class ScopedFilesystemUnmounter {
  public: